Data storage tape cartridges have been used for decades in the computer, audio, and video fields. The data storage tape cartridge continues to be an extremely popular form of recording large volumes of information for subsequent retrieval and use.
Data storage tape cartridges generally consist of an outer shell enclosure, or housing, maintaining at least one tape reel assembly and a length of magnetic storage tape. The storage tape is wrapped about a hub portion of the tape reel assembly and is driven through a defined tape path by a separate driving system. For single reel cartridge designs, a free end of the storage tape is typically secured to a leader block assembly to assist in guiding the storage tape from the housing. The housing normally includes a separate cover and base, the combination of which forms an opening (or window) at a forward portion thereof at which the leader block assembly is selectively retained.
When accessing the data stored on a storage tape in a reel-to-reel magnetic tape drive application, the leader block assembly is directed away from the cartridge housing to an area within the tape drive device where a read/write head is located. In particular, the leader block assembly is removably inserted into a drive take-up reel (separate from the data storage tape cartridge), and the storage tape from the cartridge is wound about the take-up reel as data is accessed/recorded from the tape by the read/write head. When the data storage tape cartridge is not in use, the leader block assembly is secured within the cartridge housing.
In general terms, a leader block assembly consists of a leader block and a tape clamp that secures the storage tape to the leader block. A prior art leader block 20 is illustrated in FIGS. 1 and 2. The leader block 20 includes a leading section 22 and a trailing section 24, opposing sides 34 (one shown), an exterior face 26, and an engagement surface 30. The engagement surface 30 is a smoothly curved region (as best shown in the enlarged view of FIG. 2) contiguous with opposing side 34. The leading section 22 is configured to facilitate engagement with a take-up reel (not shown) via a slot 32.
Upon final assembly, and as shown in FIG. 3, the prior art leader block 20 is engaged within a data storage tape cartridge housing, referenced generally at 42. Prior art cartridge housings typically include a cover cartridge detent 44 and a base cartridge detent 46. The cartridge detents 44, 46 are positioned adjacent a leader block window 48 and project inward into the housing 42. The cartridge detents 44, 46 retain the leader block 20 and allow it to remain seated within the housing 42. To this end, the prior art cartridge detents 44, 46 are hemi-spherical and contact the leader block 20 at exactly one point on each of the leader block engagement surfaces 30.
Upon extraction, the leader block 20 must move between the cartridge detents 44, 46 when exiting the leader block window 48. The hemi-spherical cartridge detents 44, 46 splay apart as they respond to the extraction of the smoothly curved leader block engagement surfaces 30. The cartridge detents 44, 46 impinge upon the leader block engagement surfaces 30 creating a resistance that impedes removal of the leader block assembly 20. The extraction force is proportional to the resistance. Conversely, during insertion, the leader block 20 enters the leader block window 48 and the opposing sides 34 contact the cartridge detents 44, 46. The cartridge detents 44, 46 splay apart as they respond to the contact with the opposing sides 34. The splaying of the cartridge detents 44, 46 creates resistance to the insertion of the leader block 20 that is proportional to the insertion force. Given a sufficient insertion force, the cartridge detents 44, 46 spread over the respective opposing sides 34 and engage with the smoothly curved engagement surfaces 30. Upon such engagement, the leader block 20 is seated within housing 42.
The cartridge detents 44, 46 of FIG. 3 have a limited ability to resist the removal of the leader block 20. For this reason, achieving a high extraction force can be difficult. Conversely, after extraction, the insertion force must be low enough so that the tape drive (not shown) is able to return and seat the leader block 20 into the housing 42. Because the cartridge detents 44, 46 are symmetrical, the insertion force the leader block 20 experiences when seated back into the data storage tape cartridge housing 42 is, for all relevant purposes, equal to the extraction force. Considering this, the prior art leader block 20 presents a challenging dilemma: high extraction forces will cause insertion failures, and low insertion forces lead to the leader block 20 inadvertently falling out of the housing 42.
Current leader blocks meet the needs of some data storage tape cartridge users. However, the potential exists for leader blocks having marginally high extraction forces to exhibit slippage from the data storage tape cartridge housing when shipped or dropped. Conversely, the potential exists for leader blocks having marginally low insertion forces to exhibit improper seating into the data storage tape cartridge housing. As such, a need exists for a leader block having a high extraction force and a low insertion force.